Steering Wheel Angle Determination Using Vehicle Dynamics
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Solution Overview
Problem
Existing methods for determining the absolute angular position of a steering wheel in electric power-assisted steering systems face challenges such as high costs due to dedicated sensors, limited applicability under specific driving conditions, and potential errors in dynamic parameter measurements.
Innovation Solution
A method that initializes the electric assistance motor's turns and uses a resolver-type angular sensor, torque sensor, and existing vehicle systems like ABS and ESP to calculate and continuously determine the absolute steering wheel angle, weighting values based on dynamic conditions and measurement sources for recalibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated absolute angular sensor is used to determine steering wheel position, then measurement precision and reliability are improved, but device cost and complexity increase significantly
Solution Approach 1:
The patent uses the electric assistance motor as an intermediary element to determine steering wheel position. Instead of adding a dedicated sensor, the system leverages the motor's rotor position sensor (which already exists for motor control) and combines it with mechanical reduction ratio calculations and dynamic parameter measurements (wheel speeds, yaw rate) to indirectly determine absolute steering wheel angular position, thus avoiding additional hardware while maintaining measurement precision
Solution Approach 2:
The patent makes the existing rotor position sensor serve multiple functions: it provides both the motor control feedback and the basis for determining steering wheel absolute position. The system also uses existing vehicle dynamic sensors (wheel speed sensors, yaw rate sensor) for a dual purpose: vehicle stability control and steering wheel position determination, thereby eliminating the need for dedicated steering angle sensors
2Device complexity
If statistical estimation methods are used to determine reference position, then device complexity is reduced, but reliability and applicability deteriorate under specific driving conditions
Solution Approach 1:
The patent implements a dynamic position determination system that adapts its method based on real-time driving conditions. When the vehicle is traveling straight at constant speed, it uses statistical estimation to define the reference position. When turning or accelerating/decelerating, it switches to dynamic parameter-based calculation using wheel speed differences and yaw rate. This dynamic adaptation ensures reliability across all driving conditions while maintaining reasonable system complexity
Solution Approach 2:
The system continuously monitors vehicle dynamic parameters (wheel speeds, yaw rate, lateral acceleration) and uses this feedback to validate and adjust the determined steering wheel position. The control unit compares the calculated position with expected values based on motor position and reduction ratio, and can detect errors or inconsistencies, thereby improving reliability through continuous verification rather than relying solely on static statistical estimates
3Adaptability or versatility
If dynamic parameter measurements are used to calculate absolute position, then adaptability to various driving conditions is improved, but measurement errors and calculation uncertainties increase
Solution Approach 1:
The patent merges multiple independent determination methods into a unified system: it combines the motor rotor position (from the resolver), the mechanical reduction ratio, and dynamic vehicle parameters (wheel speeds, yaw rate) into a single integrated calculation. By fusing these multiple sources of information, the system compensates for individual measurement errors and achieves both adaptability to various driving conditions and maintained precision through mutual validation of the different measurement approaches
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables precise and reliable determination of the steering wheel's absolute angular position at vehicle startup, independent of specific driving conditions, with improved precision and validity, utilizing existing vehicle systems to reduce costs and error risks.
Implementation Method 1
an angular position sensor of the rotor of the motor, of the 'resolver' type and measuring a single-turn absolute position (θmono-elec)
Implementation Method 2
a torque sensor making it possible to determine the torque exerted on the steering wheel by the driver
Data Source
AI summary
A method for determining the absolute angular position of a steering wheel of an electric power-assisted steering column of a motor vehicle, including a means for measuring a dynamic parameter while the vehicle is running and including among others, the steps of periodically determining a multi-turn relative angular position, determining at least one dynamic parameter relating to the running conditions of the vehicle using the means for measuring said parameter, determining an absolute steering-wheel angle calculated according to at least one dynamic parameter, and weighting the calculated value of the absolute steering-wheel angle according to a test of the validity of the calculated value of the absolute steering-wheel angle and the origin of said value, in other words, the measurement means used to determine said at least one dynamic parameter.